Paramecium Physiology Assignment
Winter 2021
For this assignment, you will have to design an experiment involving microscopic observation of cellular processes in
Paramecium caudatum (based upon Lab Bootcamp #2). The experimental design is up to you, but some possible suggestions or directions for your experiment(s) can be found below.
Your first step should be to formulate some research questions to which you would like to learn the answer(s). The generation of the research questions will help in the formulation of your hypothesis; a required component of any scientific experiment
. Remember that a hypothesis HAS TO TESTABLE! You can assume you will have all of the materials available to you that were present in the lab during Lab #2, if there are additional materials you would wish to use for your experiment that is acceptable (as long as it would be reasonable/realistic to acquire them).
Once again, what you investigate is up to you, the only stipulations are that you must design two different experimental conditions (if you want to do more you can but it is not required) and 1 of the two experimental conditions must be quantifiable.
Possible Factors to Consider for Your Experiment:
• Time (uptake, digestion and elimination of waste);
• Different marker sizes (ink is smallest);
• Actual food markers (yeast) versus non-food markers (ink and carmine);
• Sizes of food vacuoles;
• Numbers of food vacuoles;
• Marker concentration (more or less dilution of marker);
• Extracellular slowing agent concentration (it can be used full strength or diluted);
• Extracellular solute concentration (sugar or saline can be added to increase the extracellular solute concentration);
• Temperature (using ice/heat in experiments).
Examples of Quantitative Data Collection:
Everyone must collect some quantitative data for interpretation. Below are a couple of examples for your consideration:
● Look at a suitable number of live cells and record how many contain labelled food vacuoles at a particular time or after a particular treatment
● Count the number of marker-labelled food vacuoles in a suitable number cells
● Measure the size of the food vacuoles in fixed or slowed cells using eyepiece micrometers (stage micrometers can be provided for calibration)
● Plot the number of cells that contain labelled food vacuoles at time intervals (e.g. 3, 6, 9, 12 minutes)
List of Materials Available
You will have all of the standard laboratory materials available to you such as: glassware, pipettes, micropipettes, glass microscope slides, coverslips etc. Some additional (but Important!) materials are listed below:
1. Paramecium culture in artificial pond water
2. 1% (w/v) India Ink solution in distilled water (dilute to 1% as needed)
3. Protist slowing agent- 4% methylcellulose solution (facilitates easier viewing of living protist cells by providing a viscous medium)
4. Congo Red Stained Yeast Cells (heat killed)- phagocytotic food marker
5. Sugars (sucrose or mannitol) to modify extracellular solute concentration (could sugars have other effects beyond altering solute concentration? Be metabolized?)
6. NaCl also to modify extracellular solute concentration (how would the cell react to different solute concentrations? How does it osmoregulate?)
Note: If there is something else you would like to have available for your proposed experiment, contact your lab instructor to see if it would be possible.
Assessment (50 Marks Total):
For each of your 2 proposed experiments you will need to submit a write-up of your research proposal. These proposals should include:
Purpose/Hypotheses:
Clearly state the purpose of your experiment(s) and the corresponding hypotheses. Remember, a hypothesis needs to be testable! Ideally, the results of your experiment will either support or refute your hypothesis. (5 marks x2)
Experimental Design/Methodology:
Explain how you are going to carry out your experiment(s). This does not have to be a detailed step by step list of your procedure, but you do have to explain how it is you intend to test your hypotheses. The experimental design should be clear from this description. (15 marks x2)
Materials Required:
Provide a list of the materials and consumables needed to carry out your experiments.
